This invention relates to diagnostic x-ray apparatus. In particular, the invention pertains to programmed automatic selection of the parameters for conducting various diagnostic technics, where the data pertaining to routine x-ray technics is stored in a memory for recall and execution of control functions in response to the x-ray technologist, hereafter called the user, is accomplished by simply pressing one or a few push buttons. The values of all pertinent parameters are displayed instantaneously when a technic is selected. The invention further features anatomically coordinated user dominated programming whereby the user may resort to operation of a switch, or a few switches at most, to override the programmed parameters and introduce selected discretionary parameters of his own choice without the need to switch off the programmer entirely.
Most radiology departments follow what they consider to be consensus or standard operating procedures for various types of x-ray diagnostic examinations. For instance, for routine examination of the lungs of a series of patients in a particular radiological department and for the sake of uniformity in reading radiographs, all users would select the same x-ray tube factors such as the milliamperes (mA), anode kilovoltage (kV) and milliampere-seconds product (mAs) where the chosen tube factors would depend somewhat on the thickness of the patient. The same type of x-ray intensifying screen, the same filament and focal spot size in the x-ray tube, the same source or focal spot to film distance and possibly other parameters would also ordinarily be chosen in accordance with practices that are standardized for the particular radiology department. The parameters for various technics are often stored in the minds of the users, but they are sometimes recorded on technic charts to which reference may be made as required. If, for example, the pelvis of a thin patient were to be the subject of an examination and an anterior-posterior view were to be made, the exposure parameters could be elicited from the technic chart in order to obtain procedural standardization.
Traditionally, x-ray apparatus users were obliged to make a judgement as to the proper settings of the kV, mA, mAs, focal spot size, type of intensifying screen and so forth that is appropriate for the individual and part of the anatomy of the individual which is to be radiographed.
In accordance with the traditional methods discussed above, the user normally sets x-ray exposure parameters which, in the judgement of the user, are appropriate for that part of the anatomy which is to be examined. Usually several knobs must be turned and switches must be actuated before everything is set to produce the radiographic film density which the user desires and expects. When making the settings, the user considers all factors that might affect the exposure such as the size and thickness of the patient, the best x-ray tube focal spot size, the type of intensifying screen being used, the focal spot to film distance, and whether the direction of the x-ray beam is anterior-posterior, lateral or oblique. When an automatic exposure control (AEC) is used, the proper ion chamber or photosensor must be selected to have it fall within the x-ray field at a place that is representative of the density of the anatomy in the field central to the diagnostic area of interest. The user must also consider whether the kV, mA and mAs parameters for a technic are set to impose a safe thermal load on the x-ray tube. If the kV and mA are set too high in order to shorten the exposure interval, the instantaneous thermal ratings of the x-ray tube may be exceeded and x-ray tube life will be shortened. Attempts have been made to minimize the above identified problems by providing x-ray control systems wherein exposure parameters could be made a function of the part of the anatomy which is to be examined. The basic optimum objective was to allow the user to operate several push buttons or switches to call forth a predetermined x-ray technic. Prior anatomically based x-ray technic selectors did not achieve their intended purpose and had several problems. Firstly, too few technics were made available to cover the whole body or infrequently used procedures. Secondly, no means were provided to easily override one or more of the stored technic factors while maintaining other stored parameters or factors unchanged. When any factor other than kV had to be changed, the entire anatomical selector had to be turned off and then most factors had to be re-entered at another location. Allowing discretionary values is important in that it allows a user to follow his judgement when the condition of the patient or a medical requirement does not allow a traditional set of factors for a successful radiograph. Also, some patients are uncooperative and require specialized high speed technics to stop motion. These alternative technics were not usually available in existing purported anatomical programmers due to their limited number of stored technic programs.
Additional disadvantages of prior anatomical programmers are that their control panels lacked easy correlation of anatomical area and the control function to be selected. This situation often cancels out much of the expected convenience of an anatomically based technic selector. These was also an absence in most prior systems of the ability to program fixed time technics as well as AEC technics so a patient with a condition not appropriate for AEC, such as scoliosis, collapsed lung and the like, could not be radiographed using programmed values.
Another important deficiency in known anatomical programmers is that they are adapted for use with "decreasing kilowattage (kW)" or "falling load" x-ray tube control systems for non-tomographic procedures. In falling load systems, the kV on the tube is held constant during an exposure. In theory, the exposure begins at the full rated maximum load current on the tube. This load then begins to fall off from the initial peak during the exposure to avoid thermal overloading of the x-ray tube target. This is done by causing the tube current to decline during an exposure and by extending the duration or time of the exposure. It will be evident that the total kilowattage applied to the tube will be the integral of the product of the constant kV and the area under the declining tube current curve. Falling load generators are, however, routinely installed with de-rated initial loads of 85% of the rated tube kW or lower. So, using a constant kV, the exposure time must be extended even more than is theoretically dictated.
Moreover, the majority of x-ray technics do not require that the tube kV and mA be set at their maximums to obtain the shortest exposure time or mAs product. Thus, if unduly high mA is regularly used, reduced x-ray tube life can be expected. As is the case in most prior attempts at anatomical programming, programmers which do not provide manual control for mA may be presumed to provide a high or maximum tube current, thus compromising x-ray tube life.
A prior attempt at anatomical programming is disclosed in U.S. Pat. No. 3,916,192. It displays an outline of the human body divided into seven general zones extending from the head to the feet. A manual rotary selector switch is operated to select one of the general zones in which the anatomy of x-ray interest exists, and this first selection sets up the programmer preliminarily for determining the parameters for the technic. If the lungs were of interest, for example, the chest region is selected and visually indicated. But the chest region has bone such as the arms and spine as well as soft tissue organs. So still another selection must be made among seven more push button switches to set up the programmer for the particular technic. Thus, the maximum number of programmed technics available is 7.times.7 or 49. This patent refers to selecting and displaying radioscopic data such as kV and mA. This is not the same as selecting and displaying data for radiography as is achieved in the present invention. Radioscopy is an archaic term which has been supplanted by the term "fluoroscopy", and its use could be misleading in a discussion wherein the main topic is a programmer for producing radiographic films. No means are evident for the user to dominate or modify a single parameter such as x-ray tube current or voltage or exposure time within a particular programmed technic. Rather the user must switch off the programmer and then enter the required technic data manually. In this prior attempt, no means are provided for manually setting x-ray tube mA. Only manual kV and mAs controls are provided. Also, this prior attempt at programming technics does not provide for display of essential programmed technic parameters or data which are programmed for kV, mAs, mA and exposure time or safety time limits. Thus, a user who must adjust for an unusual patient condition must recall all of the data or refer to a published technic chart. Futhermore, the user must enter all of this data.
Other known prior patents in the realm of x-ray technic programming are U.S. Pat. Nos. 3,902,069, 3,932,759 and 3,969,625.